The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Compressors are used in a variety of industrial and residential applications to circulate refrigerant within a refrigeration, heat pump, HVAC, or chiller system (generically “refrigeration systems”) to provide a desired heating or cooling effect. Compressors may include an electric motor to provide torque to compress vapor refrigerant. The electric motor may be powered by an alternating current (AC) or direct current (DC) power supply. In the case of an AC power supply, single or poly-phase AC may be delivered to windings of the electric motor. For example, the compressor may include an electric motor configured to operate with three phase AC. The electric motor may include at least one set of windings corresponding to each of the three phases.
In each application, it is desirable for the compressor to provide consistent and efficient operation to ensure that the refrigeration system functions properly. Variations in the supply of electric power to the electric motor of the compressor may disrupt operation of the electric motor, the compressor, and the refrigeration system. Such variations may include, for example, excessive, or deficient, current or voltage conditions. In the case of a poly-phase AC power supply, such variations may include an unbalanced phase condition wherein the current or voltage of at least one phase of AC is excessively varied from the current or voltage of the other phases. Further, such variations may include a loss of phase condition wherein one phase of AC is interrupted while the remaining phases continue to be delivered. Excessive current or voltage conditions may cause the electric motor to overheat which may damage the electric motor or the compressor. Deficient current or voltage conditions, unbalanced phase conditions, and loss of phase conditions may disrupt operation of the electric motor, the compressor, or the refrigeration system and cause unnecessary damage.
The electric motor of a compressor may be equipped with a temperature or current sensor to detect overheating of the electric motor during electrical power disturbances. For example, a bi-metallic switch may trip and deactivate the electric motor when the electric motor is overheated or drawing excessive electrical current. Such a system, however, does not detect variations in the power supply that may not immediately or drastically increase the temperature of the electric motor. In addition, such systems may not detect a variation in electrical power until the condition has increased the temperature of the electric motor or the electric motor windings.
Further, such systems do not provide sufficient data to evaluate electrical efficiency of the electric motor overall. Variations in the supply of electric power may result in inefficient operation of the compressor, the electric motor, or the refrigeration system. Refrigeration systems generally require a significant amount of energy to operate, with energy requirements being a significant cost to retailers. As a result, it is in the best interest of retailers to closely monitor the supply of electric power to their refrigeration systems to maximize efficiency and reduce operational costs.